Rice protein is obtained from rice, with the starch broken down enzymatically and the remaining protein concentrated. In taste, rice protein is regarded as very mild and neutral, which is why it combines well with other ingredients.
In practice, rice protein has a comparatively low share of the amino acid lysine. Combined with pea protein, which is higher in this amino acid and somewhat lower in others, the result is a more balanced amino acid pattern. This combination is among the most commonly used blends in vegan protein powders.
The entry Multi-component protein explains more about such combinations, and the Vegan protein guide offers an overview of plant protein sources.
